Hollyhock House Art Stone Preservation

Los Angeles, Los Angeles County,
California, USA

Year of exposure to the elements were only some of the problems afflicting this classic residence. Phase I of a long-term restoration plan called for the removal and re-installation of significant portios of the upper roof and decorative elements for this early Frank Llyod Wright structure.

The Hollyhock House is Mr. Wright's earliest effort at residential housing design in Los Angeles. Phase I of this long-term restoration involved the removal, restoration, and re-installation of over 800 pieces of decorative cast stone from the parapet/roof area.

Set on a hill with a commanding view of nearby downtown Los Angeles, the house had undergone deterioration from local soils conditions, seismic activity, and inherent design flaws related to the roof and water collection systems (common with a number of Wright-designed residential projects).

Over the years of maintenance by the LA crews, several well-meaning but ultimately destructive steps were taken that advanced the deterioration process including, in this image, the application of silicone caulk around the perimeter of each decorative cast stone parapet unit. This ultimately failed in several locations as the building heaved and moved, allowing moisture to intrude and then trapping it behind areas of caulk still relatively sound.

The restoration plan called for the removal of all cast stone parapet units (approximately 600 total). Here the elaborate documentation and removal process is shown. All stones went back in the exact location from which they were removed. All location and repair information for each of 600 pieces was recorded in a database for future restoration use. Removal was achieved using small Italian pneumatic carving hammers for light impact work. The larger units shown here also required the pre-drilling of the grout joints to minimize damage to the edges of the historic material.

With an eye towards efficiency of removal, and also the safeguarding of historic building fabric, a system was devised to lower each cast stone unit to the ground as quickly and as safely as possible.

In many areas, the documentation of removed cast stone took longer than the actual removal process.

Identification tags stayed on each piece until a more permanent black ink ID number could be written on the back of each piece.

In a work area set up adjacent to the building site, each cast stone unit was first cleaned of all setting mortar and caulk.

Special holding racks were constructed for the larger cast stone units to allow for complete access to all outward surfaces, so that cleaning and abatement could be completed with the least risk to historic fabric.

A special hot water pressure washer was used to clean each cast stone unit. Custom pressure and temperature gauges allowed us to control the temperature as well as the pressure of the water stream, eliminating the chance of possible damage to the historic surface. The hot water allowed us to remove the previously applied caulk without the use of harsh abrasive techniques.

Special care was taken to store each section of wall stones together to make sure that no improper substitutions took place prior to re-installation.

Arrayed around the roof area of the house were several locations where freestanding 'Hollyhock' units were located. These were the stylistic symbols of the house's namesake flower.

Previous seismic activity had knocked over a Hollyhock stela at three of these locations.

This image shows the lackadaisical attitude of the original builders to possible seismic events. Note that the original anchor device for the missing Hollyhock is a very short piece of 1/2" pipe embedded in an already damaged planter.

New replacement units were carefully created first by moldmakers and modelers to guarantee maximum faithfulness to the originals. Great care was taken to exactly match the color and texture of the original adjacent units.

After installation, it was almost impossible to tell the difference between new and original units.

Repairs for the parapet wall cast stone units required a combination of techniques including attachment of broken elements with stainless steel threaded rod and epoxy adhesive, and patching of spalls with a cementitious patching mortar.

Repairs were completed in such a way as to eliminate any sign of intervention. Our best jobs are designed to be invisible.

Another problem solved at the site was the anchoring of the horizontal support stones for the parapet units. The support stones had shifted in several locations due to seismic activity, and these jobsite-fabricated stainless steel anchors increased the lateral resistance of the stones to movement.

They were installed in such a way as to eliminate clearance problems with the stones above and still furnish good lateral resistance in case of an earthquake.

Specialty grout injection for crack repair was performed at several locations.

There were two types of parapet stones. Here the smaller type is being re-installed. Note the passive stainless steel anchors, designed to avoid drilling holes in the actual stone. Note also the sheet metal flashing underneath each stone to eliminate future water intrusion problems.

Here the larger of the two types of stones has been re-installed in one wall area. Mr. Wright's design had us documenting material from 84 different wall surfaces.

This project only involved Phase One work, in which the roof area of the house was seismically reinforced and waterproofed. Future restoration will address other problems on different areas of the house.

This project only involved Phase One work, in which the roof area of the house was seismically reinforced and waterproofed. Future restoration will address other problems on different areas of the house.